src/Pure/General/lazy.ML
2009-09-29 wenzelm 2009-09-29 explicit indication of Unsynchronized.ref;
2009-01-10 wenzelm 2009-01-10 added force_result;
2008-12-04 wenzelm 2008-12-04 renamed type Lazy.T to lazy;
2008-10-23 wenzelm 2008-10-23 renamed structure Susp to Lazy, and Susp.delay to Lazy.lazy;